全文获取类型
收费全文 | 36854篇 |
免费 | 1953篇 |
国内免费 | 976篇 |
出版年
2023年 | 295篇 |
2022年 | 612篇 |
2021年 | 1116篇 |
2020年 | 794篇 |
2019年 | 1037篇 |
2018年 | 1251篇 |
2017年 | 986篇 |
2016年 | 1357篇 |
2015年 | 1720篇 |
2014年 | 1994篇 |
2013年 | 2447篇 |
2012年 | 2540篇 |
2011年 | 2499篇 |
2010年 | 1448篇 |
2009年 | 1210篇 |
2008年 | 1505篇 |
2007年 | 1477篇 |
2006年 | 1411篇 |
2005年 | 1228篇 |
2004年 | 1048篇 |
2003年 | 985篇 |
2002年 | 875篇 |
2001年 | 686篇 |
2000年 | 632篇 |
1999年 | 512篇 |
1998年 | 279篇 |
1997年 | 202篇 |
1996年 | 212篇 |
1995年 | 200篇 |
1992年 | 379篇 |
1991年 | 370篇 |
1990年 | 299篇 |
1989年 | 305篇 |
1988年 | 325篇 |
1987年 | 345篇 |
1986年 | 285篇 |
1985年 | 336篇 |
1984年 | 247篇 |
1983年 | 219篇 |
1979年 | 279篇 |
1975年 | 190篇 |
1974年 | 286篇 |
1973年 | 277篇 |
1972年 | 258篇 |
1971年 | 258篇 |
1970年 | 259篇 |
1969年 | 253篇 |
1968年 | 196篇 |
1967年 | 201篇 |
1966年 | 183篇 |
排序方式: 共有10000条查询结果,搜索用时 852 毫秒
31.
Zhenzhen Zhang Changjiu He Yu Gao Lu Zhang Yukun Song Tianqi Zhu Kuanfeng Zhu Dongying Lv Jing Wang Xiuzhi Tian Teng Ma Pengyun Ji Wei Cui Guoshi Liu 《Aging cell》2021,20(2)
The fecundity reduction with aging is referred as the reproductive aging which comes earlier than that of chronological aging. Since humans have postponed their childbearing age, to prolong the reproductive age becomes urgent agenda for reproductive biologists. In the current study, we examined the potential associations of α‐ketoglutarate (α‐KG) and reproductive aging in mammals including mice, swine, and humans. There is a clear tendency of reduced α‐KG level with aging in the follicle fluids of human. To explore the mechanisms, mice were selected as the convenient animal model. It is observed that a long term of α‐KG administration preserves the ovarian function, the quality and quantity of oocytes as well as the telomere maintaining system in mice. α‐KG suppresses ATP synthase and alterations of the energy metabolism trigger the nutritional sensors to down‐regulate mTOR pathway. These events not only benefit the general aging process but also maintain ovarian function and delay the reproductive decline. Considering the safety of the α‐KG as a naturally occurring molecule in energy metabolism, its utility in reproduction of large mammals including humans deserves further investigation. 相似文献
32.
33.
34.
35.
36.
Three cases of neonatal alloimmune thrombocytopenia and one patient with post-transfusion purpura could be diagnosed only by introducing the platelet immunofluorescence test. Thrombocytopenia was caused by anti-PlA1 platelet alloantibodies detected neither in the agglutination nor by the complement fixation test. 相似文献
37.
The free carboxyl group of hypermodified nucleosides N6-methyl-N6-(threoninocarbonyl)adenosine (mt6A37) and 3-(3-amino-3-carboxypropyl)uridine (acp3U20:1) in tRNAmMet (yellow lupine), and N6-(threoninocarbonyl)adenosine (t6A37) in tRNAiMet (yellow lupine) can be converted quantitatively and under very mild conditions into the respective anilides in a reaction with aniline and a water-soluble carbodiimide. The tRNA reactions proceed with rates very similar to that reported previously for t6A nucleoside. Detailed analysis of the products of tRNA modification with [3H]aniline on tRNA (chromatography on BD-DEAE-cellulose), oligonucleotide (polyacrylamide gel electrophoresis) and nucleoside (HPLC on Aminex A6) levels clearly indicates that only the hypermodified nucleoside residues undergo the reaction. The site of modification is confirmed for mono-modified (at mt6A37) and bis-modified (at mt6A37 and acp3U20:1) tRNAmMet, and for mono-modified (at t6A37) tRNAiMet by sequence analysis using 5'end 32P-labeled tRNAs. The modification procedure seems to be universally applicable for all hypermodified nucleosides bearing a free carboxyl group and for different amine reagents designed for the studies on tRNA function. 相似文献
38.
39.
40.
Dr. Benedykt Fuliński 《Development genes and evolution》1922,51(1):575-586
Ohne Zusammenfassung
Mit 2 Textabbildungen. 相似文献